1. Field of the Invention
The present invention relates to a conductive blade, and more particularly to a conductive blade for establishing charges on, eliminating charges from, or cleaning an electrophotosensitive member, a transfer drum or transfer belt used in a transfer process, an intermediate transport belt, as well as a conductive blade for smoothing charges on, eliminating charges from, or establishing charges on a developing blade used in a developing process, among others.
2. Description of the Related Art
Corona chargers utilizing corona discharge and contact chargers are among the known chargers. In a corona charger, since a high voltage of 4-8 kV must be applied to a wire, the wire and the case that surrounds the wire must be isolated from each other in order to prevent current leakage from the wire to the case. Thus, the corona charger has a drawback because of its large size. Also, since most of the discharged current flows to the case, a high discharge level is required to supply the required amount of current to an electrophotosensitive member. As a result, a large amount of ozone is generated, causing oxidation of the apparatus components and deterioration of the surface of the electrophotosensitive member, with resultant formation of unclear images. Also, such ozone may represent a health hazard.
In view of the drawbacks to corona chargers, contact chargers have been replacing corona chargers.
In contrast to the corona charger, the contact charger can charge, for example, an electrophotosensitive member at low voltage, thereby facilitating the creation of a compact electrostatographic apparatus. The amount of generated ozone is {fraction (1/10)} to {fraction (1/100)} that of the corona charger. The contact charger is configured as a conductive brush, a single-layer roller, a multi-layer roller, or a blade, among other forms.
In a conductive blade, electrical conduction between a conductive rubber member and a holder must be established, and therefore, an electrically conductive adhesive is conventionally used to connect the rubber member to the holder. However, in such a case, the bonding strength between the rubber and the holder becomes insufficient due to the low bonding strength of the adhesive. In order to solve this drawback, a conductive layer may be provided to establish an electrical connection between the rubber and the holder after they have been connected to each other in a conventional manner.
However, when the conductive layer is extended to cover the free end portion of the conductive rubber member, the length of the free end portion of the conductive blade varies, which changes the state of contact between the conductive blade and an electrophotosensitive member, or causes the rubber member to assume a wave-like form. When the conductive layer is provided on the end portion of the rubber member where the rubber member is bonded to the holder, the rubber member may assume a wave-like form depending on the material of the conductive layer. As a result, it becomes difficult to establish uniform contact between the conductive blade and the electrophotosensitive member.
In view of the foregoing, an object of the present invention is to provide a conductive blade which can maintain the planarity of a blade member and the size of the free end portion of that member even when a conductive layer for establishing electrical conduction is provided.
In order to achieve the above object, the present invention provides a conductive blade which comprises a blade member formed of an electrically conductive rubber, and an electrically conductive holder. The blade member has one widthwise end portion serving as a free end portion and the other widthwise end portion serving as a bonding end portion. One end of the free end portion is brought into contact with a subject member. The holder is bonded to the bonding end portion of the blade member over the length of the blade member. A conductive layer formed of a conducting filler and an elastomer is provided for connecting the end face of the bonding end portion of the blade member and the portion of the holder which is adjacent to the end face of the bonding end portion.
Preferably, the 300% modulus of the elastomer is 10 Mpa or less.
Preferably, the elastomer has an elongation percentage of 300% or more.
Preferably, the amount of conductive layer is 1 mg or less based on a 1 mm width of the blade member.
Preferably, the conductive layer does not substantially extend onto the front surface of the blade member opposite the bonding surface area of the blade member to which the holder is bonded.
Alternatively, the conductive layer extends onto the front surface of the blade member opposite the bonding surface area of the blade member to which the holder is bonded, and the length of the portion of the conductive layer extending along the front surface is not greater than 30% the length of the bonding surface area as measured in the widthwise direction of the blade member.
Preferably, the end of the conductive layer which is located on the front surface of the blade member is 3 mm or more apart from the edge of the bonding surface area of the blade member, the edge being located on the side of the distal end of the blade member.
In the conductive blade of the present invention, since the conductive layer for connecting the blade member and the holder is formed of a conducting filler and an elastomer, electrical conduction can be established, while the contact characteristics of the blade member remain stable.